Conversion of start stop signals to synchronous type signals and vice versa



April 17, 1945. R. E. MATHES I 2,373,970

' CONVERSION OF START STOP SIGNALS TO SYNCHRONOUS TYPE SIGNALS AND VICE VERSA FiledNov. 26, 1942 2 SheetsSheet 1 INVENTOR. um: 20 MAT/'75s BY M ATMRA/EY R. MATHES CONVERSION OF START STOP SIGNALS TO SYNCHRONOUS TYPE SIGNALS AND VICE VERSA April 17, 1945.

Filed Nov. .2 6, 1942 2 Sheets-Sheet 2 ATTORNEY Patented Apr. 17, 1945 CONVERSION OF START STOP SIGNALS TO SYNCHRONOUS TYPE SIGNALS AND VICE VER Richard E. Mathes, Silver Spring, Md assignor to Radio Corporation of America; a corporation of Delaware Application November 2.6, 1942, Serial No. 467,030

-9 Claims. -(Cl. 17870) This invention relates to electric telegraphs utilizing the Baudot code which, as is well known, has signal units of equal time-length.

There are two well-known methods of using I this Baudot code. follow each other with no intervening time space. This requires use of a commutator and brush arrangement, called a distributor, at both the transmitter and the receiver and means must be employed to keep the receiving distributor in synchronism and in phasewith the transmitting dis-- tributor.

In the other method, two additional code units, in effect, are added to each code character. On is a start unit and the other a stop unit.

' The first method -is generally employed in multiplexing by combining several telegraph channels into one composite channel for transmission either by radio or by wire, though, of course, it

is equally capable of use in single channel systems.

The second method is more generally used in single charmel systems.

There are times when it is desirable to multiplex start-stop signals with synchronous signals and also to use start-stopprinters for printing synchronous signals.

It is therefore an object of my invention to convertstart-stop code signals into synchronous signals by eliminating the start-stop units of the code and storing the code units for synchronous transmission. 7

Another object of the invention is to convert synchronous type signals into start-stop signals by adding the starting and stopping units to each code character for operation of a printer.

Other objects will appear in the following description, reference bein had to the drawings, in which:

Figure 1 is a diagrammatic illustration of apparatus for converting start-stop signals into synchronous type signals.

In one, the code characters 4 start-stop relay 2, which when energized connects the relay tongue 3 to the minus terminal for start and space and to stop.

For purposes of illustration, the start-stop printer. has been assumed to work with on-andthe positive terminal for mark and oil current, though of course plusand minus current could also be used. The spring 4 pulls the tongue to the minus terminal in response to start and space signals (no current) and the magnet, when energized, pulls the tongue to the positive terminal for mark and stop signals The tongue'3 is connected by means of a brush 5 to a slip ring 6, which is connected to brush'B on a rotating arm 9 of a distributor arrangement indicated generally by H). The distributor has four quadrants, each having five contacts I, II, III, IV, V, for the live mark or space signals, and a pair of auxiliary contacts VI, VII, through which the start and stop signals are transmitted, as will later be explained. Each contact I, II, III, IV, V is connected through condensers ll, l2, 13, M and 15 to a conductor l6,'which is grounded through resistance H, the groundbeing in this case the plus-minus terminalof the usual battery supply in a telegraph station. Contacts VI are connected as later described and contacts VII by conductor "b.

As will be noted from the drawings, the brush 8 is adapted to sweep over the contacts I to V,

inclusive, and VI in each quadrant. The brush 1 engages contact VII, only, in each quadrant. The rotating member of the distributor consists of a'switch arm 9, carrying the brushes 1 and 8. The hub of arm 8 carries four stops I8, I9, 20 and 2|, for engagement with the armature of the electromagnet 22. One terminal of the coil? connected to the brush engaging slip ring 23,

which is connected to the brush I engaging contacts VII. The armature of the magnet 22 is biased by a spring 24 to hold it in position to engage stops IB to 2|, inclusive. When the magnet is energized, the armature catch is held out of the path of the steps against the spring tension.

The contacts I to V of the distributor ID are connected to similar contacts I, II, III, IV, V of a second distributor, generally indicated at 25.

There are four quadrants to this distributor and the contacts 01' the other three quadrants are likewise connected to similar contacts of similar quadrants in distributor Ill. Distributor 25 also has'auxillary contacts VI in each quadrant, conmagnet 33 with one of the four lugs.

nected to corresponding contacts VI in distributor l0.

The distributor has a contact arm 21 bearing two properly insulated brushes 28, 29 to engage the contacts I to V", inclusive, and the contacts VI, respectively. The brush 28 is connected to a slip ring and brush 29 is connected to slip ring 3|. isconnected to channel contact 33 of multiplex distributor 34. Contacts and 35 of this multiplex distributor are connected to the two other channels of a three channel multiplex transmitting system, which for pun-poses of illustration we may assume to be connected to a tape transmitter 01' to some other signaling device, the character of which obviously will not aflect the Brush 32 engaging slip ring 30 operation of the system being described. Brush 31 engages a slip ring connected to the rotating distributor brush 31a successively engaging channel contacts 33, 35 and 38. Brush 31 is connected to the outgoing line Lthrough a locking circuit type keyer 31b of any desired type.

The coil of magnet 38 has one terminal connected to the minus terminal of the supply battery'and the other terminal is connected to contact 39 on the armature of this-magnet and to the brush 40 engaging slip ring 3|. The other contact 4| of the magnet switch is connected I through switch 42 t0 the positive terminal. The

armature of magnet 38 is biased to open position of the switchby a suitable spring 43, in which position it is free of lugs 44, 45, 45 and 41. The other end of this armature, when the magnet is energized, is in position to be engaged by these four lugs. The arm 21 and itsfour stop lugs of distributor 25 are rotated through friction slip-clutch 48, shaft 49, gear box 50, shaft 5i, gear box 52 and motor 53, so that the shaft 43 of the distributor 25 is run at a speed proportional to the speed of the multiplex distributor arm 54, which as shown is connected to the shaft of the motor 53.

Since, in a three channel system, the outgoing line L is assigned to one transmitting channel only once a revolution of the distributor brush arm, shaft 49 would rotate at such proportional speed that the arm 21 would move the angular distance between the adjacent two of contacts I, II, III, IV, and V','while the distributor arm makes one complete revolution. The shaft 55,

however, runs at a slightly greater speed than the start-stop sender I, as is standard printer practice. This shaft also runs at the same speed as,

or slightly faster than, the shaft 49. Therefore, arm 21 cannot overtake arm 9 while both are rotating. It can catch up with it after a definite armature of magnet 22. Friction clutch 48 has a similar purpose in distributor 25 when the arm 21 is stopped by engagement of the armature of However, as will be noted, the rotation of the arm of distributor I0 is stopped only when the magnet 22 is de-energized and the arm of distributor 25 is stopped only when the magnet 33 is energized. Also, magnet 22 is made slow-acting, while magnet 33 is made quick-acting, for reasons that will later be referred to.

Switch 42 is opened by a cam wheel 51 having four cam notches equi-spaced around its periphery. This cam wheel rotates at a speed proportional to'the speed of the arm and lugs of distributor 25 when they are not stopped by the armature of magnet 33, but this speed will be such that the switch 42 is opened once while thearm 21 is traveling through one of the quadrants. That is, the cam 51 and arm 21 have the'same angular speed. The switch assembly 42a is mounted for adjustment around the periphery of the cam wheel 51. Screw 42b peened in the flange 42c (sectioned inFig. 1) and threaded through sta tionary lug 42d permits adjustment of the time of opening of the switch 42.

The gear boxes and 52 may be constructed in any way to secure the proportional speeds for operating the arms of distributors I0, 25 and switch 42.

The operation of the transmitting system of Fig. 1 may be described as follows:

Let it be supposed that theoutgoing signals of the start-stop printer are to be multiplexed in with the signals of the two other channels. When the start signal is sent out from printer I (no current), spring 4 will cause tongue 3 to engage the minus terminal. This will close the circuit from the plus terminal through the coil of relay 22, brush and ring 23, brush 1, contact VII, conductor I12; and tongue 3 to the minus terminal. This will release the catch from its lug, 28 in this case, and the distributor arm 9 will immediately start rotating at the speed of shaft55. The coil of magnet 22 is made so as to release in time for the brush 8 to pass over contact I substantially in the center of the first code signal pulse as it arrives from the start-stop printer I. This may be either a space or a mark signal. In either case, condenser II will be charged, but its polarity for a mark will be the reverse for that of a space. The rotating arm of distributor 10 will be running at the same speed as, or very slightly faster than, the cam in the start-stop sender l and therefore the condensers l I, l2, l3, l4 and I5 will be charged with one polarity or the other by the mark or space signals sent out. When the arm 9 reaches contact VI, the stop signal (current) is sent out by the transmitter of start-stop sender I. This stop signal is not sent out over the multiplex distributor, as it has no significance in a synchronous system, but it makes the tongue 3 positive and current will not flow through the coil of magnet 22, since both terminals are positive. The armature catch'of magnet 22 therefore engages the next stop lug l9 by action of spring 24.

4 During the movement of the arm of distributor l0 through the quadrant as just described, condensers Il, I2, 13, i4 and 15 were charged with one polarity for mark signals and the other polarity for space signals. Let it be supposed that when the arm 9 was at some intermediate position in that quadrant, say with the brush 8 on contact IV, notch 60 on cam 51 opened the switch 42. This de-energized the magnet 38 and the spring 43 moved the armature catch away from the stop lug 44. Therefore, as the arm 9 of distributor Ill continued its rotation from contact IV in the quadrant, as already described, arm 21 of distributor 25 commenced its rotation. When the brush 28 was brought into position with contact I, condenser ll discharged through contact I, brush 28, ring 30, brush 32, contact 33, distributor arm 54 and brush 31 to the locking circuit keyer and outgoing line L. Thus, rotating arm 21 passed the charge of the'five condensers in each quadrant and the signals went out over the line L.

Since arm 21 ot distributor 25 rotates at a speed proportional to that o! multiplex arm 54, the distributor brush 81a always will be in engagement with the contact 88 when the brush 28 engages each of the contacts I to V, inclusive, due to proper adjustment of screw 42b.'

Soon after the stop signal was sent out by the start-stopprinter I, as already described, the

start signal is transmitted. This places the tongue {in contact with the minus terminal and magnet 22 is energized by current passing from the positive terminal through the colic! magnet 22, brush and ring 28, brush I, contact VII and tongue 8, to the minus terminal. The armature is therefore released fromcontact with the lug l8.

' until it catches up with arm 8. Magnet 88 can never be energized to stop arm 21 from rotating unless brush 28 engages contact VI when brush 8 is in engagement with contact VI in the same quadrant. Only at that time can current flow through the magnet 88, for positive potential is i applied to the contact VI, with the tongue 8 in engagement with the positive terminal at relay 2, due to the stop signal. The energization of the stop relay causes the armature catch to engage one of the lugs .44, 45, 48 or 41 and stop the rotation of arm 21. Ordinarily. a number of revolutions of arm 27 will be completed before this occurs. When magnet 88 is energized in this way, the holding circuit is closed from the positive terminal through switch 42 and contacts 89 and H, which are now closed. Soon thereafter the start signal (no current) is sent out by the start-stop printer and armature 8 again starts to rotate by energization of magnet 22. This, however, does not de-energize the coil of magnet 88, due to the a holding circuit just referred to, and arm 21 of distributor 25 will remain at rest while distribu tor arm 8 proceeds to rotate and charge up con- .densers II to l5, inclustlve, in the succeeding quadrant.

At some point cam 51 will bring a cam notch into position to open switch 42 and magnet 88 I will be de-energized. This will start distributor arm 21 again on its rotation, after which it will again catch up with the distributor arm 8 and be stopped. as previously described.

While the distributor arm 21 is stopped by err-- ergizatlon of magnet 88, no signals will be sent out to line L when the multiplex distributor arm 54 brings its brush into engagement with contact- 33, but since this magnet is energized only when the brush 8 of distributor arm 9 is on contact VI, all five signal elements of a letter or other-code character will have been transmitted and a code character cannot be mutilated,

In. this 'way the distributor arm 21 will be stopped when it catches up with the distributor arm 8 and then will be held up for substantially asraavo three channels connected to contacts 88, 85 and 88 in Fig. 1 and converting them into start-stop signals so that they may be printed on a startstop printer, but of course,- similar apparatus could be used to convert the signals of all three channels into start-stop signals.

, In Fig. 2 the composite signals sent out by the and it will be assumed to receive the signals sent out by the start-stop printer from contact 83 ,on the transmitting distributor, though they equally could nel.

The distributor arm 62 will be rotated in synchronism with the transmitter distributor by wellknown means, generally indicated by motor 85. and synchronized and phased in well-known ways (not shown) The five start-stop code units sent be the signals from any other chanout by the transmitter will be received in succession with no time separation between the end of one code character and the beginning of the next.

Since these are to be used to operate a start-stop printer, means is provided for inserting start-stop signals in appropriate places in the cycle.

The flve synchronous code units will be sent into a locking circuit 65a for regeneration of the signals. Such a locking circuit is well known in the art and is therefore indicated herein only in block diagram. Such a locking circuit is shown in detail in the patent to John W. Cox, No. 2,264,510, December 2, 1941, and the theory of operation is described therein. It will be-suillcient to say herein that the terminals of the locking circuit produce a potential drop across resistance 88 oi. one polarity for marks and another polarity for spaces. The positive terminal of the supply voltage is connectedto the midpoint in this resistance. One terminal of resistance 86 is connected to brushB'I contacting with slip ring 68 on a distributor generally indicated 'at 89. The other terminal oi resistance 86 is connected through the coil of relay 18 to brush ll engaging slip ring 12. Slip rings58 and 12 are secured in any way t arm 18 of the distributor 88, which rotates at one-fifth the speed of the distributor arm 62. Distributor arm I3 carries brush I4, adapted to engage th live equally-spaced contacts I5, 16, 11, I8 andl9, when multiplex distributor brush 63 is on contact 84. The five "contacts are shown virtually as segments of a circle, separated at the ends by strips of insulation, but in practice these segments would be shortened so that they would be one-half to one-.- iourth the angular length oi the time signal, as is usual in telegraph distributors. Contact I5 is connected by a conductor 88 with contacts I1 and 18, while contact I8 is connected by conductor 8| with contact 18.

upp end resistance- 6 is connected through condenser 82 to conductor and through condenser 88 to onductor 8|.

Distributor 69 has seven arcuate contacts 84. 85. 88, 81, 88, 89 and 98. shown as having substantially equal length and separated by strips of insulation at adjoining ends. 'I'hese contacts are p"eferably arranged to be adjustable as a unit around the inner contacts 15 to 18, inclusive.

This is indicated conventionally by the screw mechanism 80a. These contacts preferably would be shortenedin practice in the same way as conthe telegraph supply battery,

tacts 15 to 1.8. Contact 84 constitutes the start contact and lags contact I8 in relation to the rotating arm 13, but overlaps such contact. This contact is connected to the minus terminal of Contact 88v is connectedto the inner contact 15, contact 88 to the next inner contact 16, contact 81 to inner.

contact I1, contact 88 to inner contact 18, contact 88 to inner contact I8 and contact 88 to the positive terminal of battery 8|. I

The relay 10 is polarized because it has been assumed that the locking circuit 68:: places alternate plus and minus potentials in resistance 88. Of course, on-and-ofl potentials could have been produced in this resistance by the locking circuit with the positive terminal and in theother position with the other terminal that has no potential. The start-stop printer 88 has been assumed to work on on-and-ofl current, but it could equally well operate on plus and minus current in which case the blank terminal of relay 18 would be connected toa minus potential. The tongue 82 of the relay is connected in the usual way to one terminal of the start-stop printer 83, the other terminal of this printer being grounded to the plus and minus terminal of. battery 8!.

The operation of the receiving circuit in Fig. 2 may be described asiollows:

The incoming synchronous signals are separated by the distributor arm 82 in a well-known way and produce plus or minus potential drops in resistance 88 and these potentials will be produced in synchronism with the movement of the rotating distributor arm 13. When brush Ila on distributor arm 18 engages outer contact 88, current will flow from battery 8! through contact 88, brush "a, slip-ring l2, brush H and the coil of relay 18, back to the mid-terminal of the battery. This will throw the relay tongue 82 against the positive contact, which will produce a stop signal for the start-stop printer. The first code unit of a character will be received soon thereafter and wili'produce a potential in resistance 88 while the distributor brush H is on contact 18. This will produce current flow through brush 81, relay ring 88, brush 1, contact I5, conductor 88 and condenser 82 to the other terminal of the resistance. The polarity of the charge in condenser 82 will, of course, depend upon the character of the signal being received. If it is a mark, the condenser will be charged with one I polarity, and if a space, an opposite polarity.

The brush Ilanext engages contact 84 and current flows from the midpoint terminal of battery 8| to the lower end of the coil of relay I8, through brush ll, ring 12 and brush Ila to the minus terminal of the battery. This will energize relay 18 in an opposite direction and throw tongue 88 through brush 61, ring 88, brush [4, contact" 18, conductor 8| and condenser 83 to the other terminal of resistance 68. The first and second signals of the code character are now stored in condensers 82 and before the distributor brush Ha engages outer contact 88. When contact 85 is engaged by the brush 14a, condenser 82 will discharge through conductor 88. contact 88, brush "a, distributor ring 12, brush II and the coil of I relay 18 back through conductor 88 tothe Other terminal of the condenser. Therelay tongue 82 will then be positioned either against the positive contact or the blank contact,- depending upon the polarity ofthe signals stored in this condenser.

- will be in position for receiving the first code unit and will operate the first selector 'bar in one direction or the other.

When the distributor arm 18 passes oi! of inner contact 18, it will engage contact 11 and charge condenser" in a way already described.

Slightly before this time, brush 14a. will engage the outer contact 88 and permit the discharging of the second code unit stored in condenser 88 through the coil of relay 18. This will pass through conductor-8|, contact 88, brush "a, slip ring 12. brush H, the coil of relay l8 and conductor 88 to the other terminal of the condenser.

This will position the tongue 82 against either.-

the positive contact or the blank contact, de-

pendent upon the signal. The start-stop printer reaches the second code position when the brush Ila is in the middle of contact 88 and the second selector bar will be thus moved in response to either a mark or a space signal.

when the distributor arm moves the brus Ha onto outer contact 81, condenser 82 dis,- charges through the. coil of relay 10 and throws the tongue 82 onto the positive contact for a mark or onto the blank contact for a space. This is the stored signal of the third code unit and will cause the printer 83 to move the third selector bar when the third code position of the printer is reached,

As the distributor arm 13 continues to rotate, brush I4 engages contact 18 and the incoming fourth signal is stored in condenser 88. The distributor arm 13 next brings brush 14a onto outer contact 88 and the fourth signal unit just stored in condenser 83 discharges through the coil of relay [8 in position to cause the selection of the fourth selector bar in printer 83.

The distributor arm I3 then brings brush it into engagement with inner contact 18 and stores the fifth signal code unit in condenser 82 and when brush 14a engages the fifth contact 88', this condenser discharges through the coil-of relay 10 to produce the movement ofthe fifth selector bar in the start-stop printer.

When the distributor brush Ha engages the outer contact 88,'a stop signal is produced in the start-stop printer 83, as already. described. The reception of one character and its printing has now been completed. The signal code units of the second character will be stored and cause the operation of the printer 83, in theway already described. I

It usually will not be necessary to store the fourth and fifth code units in the condenser, as the brush Ha will usually be on the outer contacts 88 and 88 to permit the received signal cur-. rent to pass directly through the coil of relay 18. However, it is preferable to connect all live contacts to condensers 82 and 83 and to interconnect the inner contacts with the outer ones, as described, so that the printer will operate either directly from the received signals or from such signals stored in'the condensers, and it is leaves oif. I

I have shown one embodiment for converting start-stop signals at the transmitter into synchronous signals andjor converting synchronous signals at the receiverinto'start-stop signals, but it will be apparent that various modificationsmay be used without departing from the spirit of the invention.

described my invention, what I claim is:

1. In apparatus for transmitting code unit signals from a-start-stop sender through'a' single channel to the composite channel of a time division multiplex system, separate sets of independent storing devices for the code unit signals of a plurality of characters, means for convey- 2,373,970 immaterial where one commences andthe other ing the code unit signals from said sender to I signals from a start-stop sender through a single channel to the composite channel of a time division multiplex system, separate sets of independent -condensers for storing the code unit signals of a plurality of-characters, means for storing the code unit signals of a character in the condensers of one of said sets insuccession, means for discharging said condensers in succession through the single channel in synchronism with its assignment to the composite channel while signals are being stored inthe condensers of another of said sets, means for stopping the operation of the second-mentioned means upon the discharging of all of the charged condensers.

3. In apparatus for transmitting code unit signals from a start-stop sender through a. single first switch arm upon receipt of the start and stop signals, respectively, from said sender, a

second movable switch arm connected to said single channel for relaying nals of one of said sets while signals are being stored in another of said sets, means forstope ping the operation of the second switch arm upon its overtaking the first switch arm in stopped '0 annel to the composite channel oia time division multiplex system, separate sets of contacts and connected storing devices for the code unit signals of a plurality of characters, a first switch arm connected to said sender and moving over said contacts in succession for conveya single channel and adapted to move over said additional contacts for relayingin synchronism through said composite channel the stored sig-v nals of one of said sets'while signals are being stored in another of saidsets, means for stopping the operation of the second switch arm upon its overtaking the first switch arm in stopped position and restarting it after the first arm has again started and has moved over substantially all the contacts of another set.

6. In apparatus for transmitting code unit signals from a start-stop sender through a single channel to the composite channel of'a time division multiplex system, a receiving distributor having a switch arm and a plurality of groups channel to the composite channel of a. time division multiplex system, separate sets .of contacts and connected storing devices for the code unit signals of a plurality of characters, a switch arm connected to said sender and moving over said contacts in succession for conveying the code unit signals of the characters to the storing devices of one of said sets, means for relaying the stored signals of one of said sets while signals are being stored in another of said sets in succession through the single channel in synchronism with its assignment to the composite channel, means for stopping the operation of the second-mentioned means upon its relaying all of the stored signals and restarting it upon the first-mentioned means storing additional code unit signals in another of said sets.

4. In apparatus for transmitting code unit signals from a start-stop sender through a single channel to the composite channel of a time division multiplex system, separate sets of contacts and connected storing devices for the code unit signals of a plurality of characters, a first switch arm connected to said sender and moving over said contacts in succession for conveyof contacts, each group having a storing contact for each unit of the code and a first and a second stop contact, storing means connected to each storage'contacts, said switch arm having a first and a. second brush, the first brush being adapted to engage the storing contacts and the first stop contact in succession and the secondbrush being adapted to engage the second stop contacts in succession, a relay adapted to be enbrush and to said second stop contacts, meansfor rotating said switch arm, a magnet having its coil connected to the second brush and having an armature for stopping the rotation of said arm, a repeating distributor having a switch arm, a plurality of groups of discharge and stop segments, the discharge and stop segments of each group being respectively connected to corresponding storing and first stop contacts of a group in the receiving distributor, a second stop magnet, a holding circuit for the coil of said magnet, a first and a second brush on the repeating switch arm, the first brush being connected to said single channel and adapted to engage the discharge segments and the second brush being connected to the coil of the last-mentioned magnet and adapted to engage the stop segments, and means for opening said holding circuit a'predetermined time before the" said channel is assigned tosaid repeating distributor.

7. In apparatus for transmittingv code unit signals from a start-stop sender through a single in synchronism through said composite channel the stored sigchannel to thecomposiie channel oi a time division multiplex system, a plurality of sets ofstoring devices, each adapted to store thesignal units of a code character independently of the other sets, distributing means for storing signal relaying means for transmitting the stored signals through said single channel and means for startingsaid relaying means into action only upon said distributing means substantially completing the storing of the units so! a code character.

' 8. In apparatus for transmitting code unit signals from a start-stop sender through a single unlts of a character in said sets in succession,

asrsmo uting means substantially completing the storaseoitheunitsotacode characterinsaidcondensers.

9. In apparatus for transmitting code unit. signals from a start-stop sender through a single channel to the composite channel of a time division multiplex system, a plurality of sets of storing devices, eachadapted to store the signal units oi a code character independently of the other sets, distributing means for storing signal units of a character in said sets in succession. relaying means for transmitting the stored signals through said single channel, means for starting said relaying means into action only upon said distributing means substantially completlng the storing of the units of a code character.

acter, the average ,rate of relaying said signals being faster than the average rate oi storage thereof and means for rendering the relaying means inactive upon relaying of all stored signals until the distributing means again stores substantially all the units of the next code char- RICHARD E. MATHES. 

